Academic journal article Attention, Perception and Psychophysics

Top-Down Influences Mediate Hand Bias in Spatial Attention

Academic journal article Attention, Perception and Psychophysics

Top-Down Influences Mediate Hand Bias in Spatial Attention

Article excerpt

Published online: 31 May 2013

© Psychonomic Society, Inc. 2013

Abstract Spatial attention can be biased to locations near the hand. Some studies have found facilitated processing of targets appearing within hand-grasping space. In this study, we investigated how changing top-down task priorities alters hand bias during visual processing. In Experiment 1, we used a covert orienting paradigm with nonpredictive cues and emphasized the location of the hand relative to the target. Hands or visual anchors (boards) were placed next to potential target locations, and responses were made with the contralateral hand. Results indicated a hand-specific processing bias: Hand location, but not board location, speeded responses to targets near the hand. This pattern of results replicated previous studies using covert orienting paradigms with highly predictive cues. In Experiment 2, we used the same basic paradigm but emphasized the location of the response hand. Results now showed speeded responses to targets near response locations. Together these experiments demonstrated that top-down instructional sets (i.e., what is considered to be most relevant to task performance) can change the processing priority of hand location by influencing the strength of top-down, as compared with bottom-up, inputs competing for attention resources.

Keywords Spatial attention · Cue predictability · Embodiment · Top-down · Task relevance · Multisensory integration

Recent spatial attention studies have demonstrated attention-al biases for visual stimuli presented near the hand (Reed, Betz, Garza, & Roberts, 2010; Reed, Grabb, & Steele, 2006). In experiments using covert orienting paradigms with predictive cues, speeded response times are observed for targets appearing near the hand, rather than for targets on the opposite side of the display. These results suggest the additional contribution of visual-tactile bimodal processes to visuospatial processing for the region of space near the hand, as well as proprioceptive inputs indicating hand location. Furthermore, the topography of the attentional bias near the hand appears to be related to functional capabilities of the hand. The bias is strongest for targets appearing in grasping space next to the palm, as compared with equidistant locations behind the hand or near the forearm. Together, these studies suggest that the ability of the hand to perform actions on nearby objects affects the distribution of spatial attention.

An open question is whether the hand's biasing of attention is affected not only by additional perceptual contributions, but also by task expectations. The selection of contending objects by visual attention is a competitive process among sensory-related bottom-up inputs and top-down sources of control to direct attention to particular objects or spatial locations (Kastner & Ungerleider, 2000). Bottom-up neural mechanisms are largely automatic and select on the basis of stimulus features (e.g., luminosity). Multimodal perceptual inputs from visual, proprioceptive, and tactile systems about hand position may act together to increase their salience in the selection process. Top-down mechanisms bias this selection to objects relevant to current behavior and goals. The placement of the hand can bias goal-directed behavior because its location and grasping function suggests that a stimulus near it may be important for upcoming action. Thus, a hand positioned in a particular location in the visual field is likely to influence attention from both bottom-up and top-down directions. Although recent work has argued that the effect of the body on visual processing may be attributed to early sensory-related pro- cessing (e.g., bimodal neurons, figure-ground segregation; Cosman & Vecera, 2010; Reed et al., 2010; Reed et al., 2006), little work has investigated how top-down influences and task expectations interact with the hand's effect on visual attention.

We investigate how top-down influences, such as cue predictability and instructional set, might alter the hand's influence on spatial attention. …

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